The invention is directed towards the field of electronic circuitry, and more specifically, towards ergonomic input devices such as a computer mouse.
Repetitive Strain Injuries (RSI) are a modern-day hazard in the computer-using workforce, and are a leading cause of occupational injuries in the United States today. Computer mouse usage is blamed for many of these injuries. A mouse is typically used as an input device that controls the movement of a cursor or other display element on a display screen. The conventional and most commonly used mouse resembles a bar of soap in shape and size. This xe2x80x9csoap barxe2x80x9d mouse is designed such that a user""s palm and fingers rest on the mouse body when moving the mouse or activating its buttons. A primary and a secondary switch are positioned on top of the mouse, adjacent to each other. The primary switch is activated by the first finger and the secondary switch is activated by the second finger. Unfortunately, this design requires the user""s fingers to be splayed out over the mouse body and buttons, instead of being slightly curled in as is natural when the hand is relaxed. Furthermore, the hand is completely pronated (rotated so that the palm faces down, parallel to the desk top) while working the mouse. This unnatural position strains the tendons in the hand, and can be harmful especially when maintained for an extended period of time. A more natural and ergonomic position for the hand is one where the palm and wrist are 45xc2x0 to 90xc2x0 less twisted.
Another drawback to the conventional mouse is the awkward movements required to activate the switches. The primary switch on a conventional mouse is designed to be activated by a tap of the first finger in an up-down motion substantially perpendicular to the work surface. However, this requires the first finger to be flexed repeatedly while the hand is pronated and the first finger splayed out. This motion can strain the finger tendons. For example, when the primary switch is activated, the user must keep the second finger stationary in its outstretched and splayed position while the first finger presses down upon the primary switch. The reverse is also true: when the secondary switch is activated by the second finger, the user must hold the first finger still to prevent it from inadvertently activating the primary switch. This unnatural muscle restraint, especially among adjoining fingers, is uncomfortable and may also increase the risk of RSI.
The xe2x80x9csoap barxe2x80x9d mouse typically uses a mechanical ball bearing mechanism to sense motion along the work surface. However, the mechanical ball bearing mechanism is physically large, requiring a mouse with housing large enough to contain it. The motion of the mouse is typically controlled by hand and arm muscles, which have relatively poor fine motor control. Therefore, a third drawback to the xe2x80x9csoap barxe2x80x9d mouse is its unwieldy shape and relatively large size, which make it relatively difficult to control the mouse with the high degree of accuracy required by many Computer-Aided Design (CAD) tools.
Consequently, there remains a need for an ergonomic computer mouse that has accurate positioning capability and alternative methods for switch activation, while allowing a user""s hand to remain in a natural, relaxed position. The ergonomic mouse should also support three modes of positioning determined by the inventor to be important for heavy mouse users such as users of CAD software: gross motions produced by moving the arm, finer motions produced by anchoring the hypothenar (the fleshy region of the palm under the little finger), and even finer motions produced by nudging the mouse using the fingers.
The general idea for the present invention was partially derived by observing the writing process, and in particular, the way one holds a pen or an eraser. (Exemplary erasers are Pink Pearl(copyright) or Magic Rub(copyright) erasers made by Sanford, or any other erasers having a size comparable to the present invention.) Writers use an inherently ergonomic hand position, hereinafter referred to as the writing position: the fingers remain curled, not splayed out; the hand is angled between 45 degrees and 90 degrees to the work surface, never completely pronated; and the hypothenar of the hand rests on the work surface. Additionally, the number of RSI cases associated with writing is relatively low, compared to the number of computer-related RSI cases. Therefore, it is logical and reasonable for an ergonomic mouse to recreate the hand positions and motions used in writing or holding an eraser.
In accordance with an illustrated preferred embodiment of the present invention, an ergonomic mouse has a small body designed to be gripped between the thumb, first finger, and the second finger of the hand, similar to how a writing implement or an eraser is held. This allows the hand and fingers to remain in the natural and relaxed writing position while the hypothenar rests on the work surface. The fingers rest curled inwards and close to each other, rather than being splayed uncomfortably across the mouse body as with conventional mice. The small size of the mouse serves primarily to facilitate dexterous use and control by the fingers, the same way one uses a pencil. Since deft finger muscles control the mouse, it is possible to position the mouse very accurately. Furthermore, the small size of the mouse is well suited to the limited amount of space associated with laptop computers. The small size of the mouse is made possible by using an optical sensor instead of a conventional mechanical ball bearing that takes up more space.
The primary switch, located on an angled facet of the mouse, is activated by the first finger. The angled facet allows the first finger remain curved while approaching the switch from a more natural angle. The angle of the facet may vary, but is preferably between 30 and 70 degrees to the vertical, and angled towards the upper right corner of the mouse. If the size of the facet allows, more than one switch may be located on the angled facet. The first finger rests on the facet while manipulating the mouse. The adjoining second finger grips one side of the mouse body in a curved position. Since the second finger is not positioned over a switch, there is no need to isolate its motion from that of the first finger. Depending on the size of the user""s hand, there may also be enough room on the side of the mouse body to accommodate the third finger for extra grip control. A secondary switch is positioned on another side of the mouse body, opposite the side where the second finger rests. The secondary switch is activated by the thumb with a pinching motion between the thumb and the second finger (and possibly the third finger if space allows) resting on the side. This switch preferably requires a slightly higher actuation force than the primary switch, so that merely gripping the mouse will not cause it to be inadvertently activated.
Besides preventing RSI, the present invention also gives the users facile control of the mouse, by supporting three modes of positioning observed by the inventor: gross motions made by moving the arm, finer motions made by anchoring the hypothenar, and even finer motions made by nudging the mouse using the fingers.
Further features and advantages of the present invention, as well as the structure and operation of preferred embodiments of the present invention, are described in detail below with reference to the accompanying exemplary drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.